If it launched with a killer game (and it'd have to be something akin to a new 3d mario game) day one...otherwise next time I'll wait for some good games...
Have bought the last 3 nintendo consoles the day they were released (and the gba and ds as well) and have learned my lesson...obviously it took a while.
Am sick of buying nintendo machines then waiting a year or 2 for a decent game to come out!
(to be fair, the same thing happens with most systems, not just nintendo...so sorry for singling them out!)